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In total, there are about 261.3 acres included in the watershed, which includes about 98.5 acres <br />of disturbance. Much of the pond is in areas of approximately 20 feet of excavation as shown on <br />the cross-sections provided on Exh. 7-23, Figure J2. Above elevation 7220, cut slopes will be <br />constructed at 2H:1 V side slopes. <br />For the first SEDCAD model, it can be seen that the 10 year, 24 storm event with 1.8 inches of <br />precipitation resulted in about 5.9 acre-feet of runoff and a peak flow of about 68 cfs. Since the <br />design capacity of the pond somewhat larger, the structure has approximately 0.9 acre-feet of <br />excess capacity. The annual (one-year) sediment yield from the entire watershed is <br />approximately 0.10 acre-feet. <br />For the second SEDCAD model, the 25 year, 24 hour storm event of 2.3 inches of precipitation <br />resulted in the a peak flow of about 111 cfs and a total runoff volume of 10.3 acre-feet. Flow <br />depth through the emergency spillway is approximately 0. 16 feet. <br />The following SEDCAD models accompany this submittal. <br />• Temporary Sump, 10 year, 24 hour event <br />• East Collector Ditch, 10 year, 24 hour event <br />• West Collector Ditch, 10 year, 24 hour event <br />• Coal Stockpile Pond, Complete Containment, 10 year, 24 hour event <br />• Coal Stockpile Pond, Complete Containment, 25 year, 24 hour event <br />Exh. 7-23M-3 Revision Date: 5/17/17 <br />Revision No.: TR -111 <br />